Carbon Equivalent Value CEV
The IIW carbon equivalent value quantifies the influence of various alloying elements on the hardenability and cold cracking susceptibility of unalloyed and low-alloy steels. It serves as a safety-oriented basis for determining preheating temperatures prior to welding.
The carbon equivalent is a calculated value that tells you how hardenable a steel is. The higher the value, the more sensitive the steel is to rapid cooling and the greater the risk of cold cracks in the heat-affected zone. If the value is high, you must preheat the steel before welding and slow down the cooling. With low values, you need to worry less, but never forget that other alloying elements also play a role. When in doubt, always check the data sheet or ask the supplier which value applies to your steel. And remember: a clean, dry workpiece and proper preheating are half the battle against cracks.